Trypanosoma cruzi ubiquitin as an antigen in the differential diagnosis of Chagas disease and leishmaniasis.

In the present report we describe Trypanosoma cruzi ubiquitin as an antigen to be utilized in the differential diagnosis of Chagas disease and leishmaniasis. Initially, recombinant T. cruzi ubiquitin was evaluated against a panel of sera by phage dot immunoassay, showing a good performance against chagasic sera. However, the presence of a carboxy-terminal tail region encoding a ribosomal protein homologous to a related protein present in the genome of Leishmania sp. gave significant cross-reactivity with leishmanial sera. Therefore, ubiquitin was purified by a simple biochemical protocol and its immunoreactivity was studied by enzyme-linked immunosorbent assay. Analysis of 104 sera indicates that the response to ubiquitin is very sensitive towards chronic chagasic sera (98%) and, more important, highly species-specific, presenting better performance compared to the use of the recombinant protein or the total epimastigote extracts when tested against a panel of leishmanial sera, where out of a total of 70 sera tested, only five sera from the mucocutaneous form of the disease reacted with T. cruzi ubiquitin. On the other hand, Leishmania ubiquitin was not recognized by chagasic sera, but was recognized by sera from different forms of leishmaniasis. These results make ubiquitin an excellent candidate to be used in the differential diagnosis of these two parasitic diseases. The molecular basis for this highly species-specific response is discussed.